Vapor-electric device



Nov. 4, 1952 LEWlN 2,617,064 I VAPOR-ELECTRIC DEVICE Filed Oct. 12, 1950INVENTOR GEAH/IAD ZFI W/V.

ATTORN EY Patented Nov. 4, 1952 UNITED STTES.

VAPOR-ELECTRIC DEVICE Application October 12, 1950, Serial No. 189,784

11 Claims.

This invention relates to vapor-electric devices such as are generallyknown as ignitrons.

Attempts have heretofore been made to provide a semi-solid or spongecathode for electric discharge devices, and the present inventioncontemplates improvement thereover.

In the broad aspects of the invention, more stable and unfailing aredischarge is an objective and accomplishment thereof.

The invention also provides for the-more effective cycle of vaporizationat the point of arc instigation of the reconstructing liquid cathodematerial, condensation and return to the initial point of arcinstigation.

The invention further provides for copious supply of the liquid cathodematerial at the point of arc instigation.

Another object of the invention is to provide a sponge cathode that willgulp in, as fast as available, all liquid cathode material condensing onor flowing to the sponge cathode, and yet make the liquid available atthe surface where the arc strikes.

Other objects of the invention will appear to those skilled in the artto which the invention appertains as the description proceeds, both bydirect reference thereto and by implication from the context.

Referring to the accompanying drawing, in which like numerals ofreference indicate similar parts throughout the several views:

Fig. 1 is a central longitudinal sectional view of an ignitron ofarbitrarily selected construction showing my invention embodied therein;

Fig. 2 is a cross-section on line IL-II of Fig. 1;

Fig. 3 is a sectional view of the sponge cathode alone;

Figs. 4 and 5 are similar sectional views of modified constructions ofsponge cathodes; and

Fig. 6 is a similar sectional view of a modified construction of discfor the firing area of the cathode.

In the specific embodiment of the invention and associated ignitronconstruction illustrated in the drawing, but without limiting to thedetails thereof, a cylindrical casing of steel or other sturdy materialis shown having a bottom I2 integral therewith and a top header l3sealed at the upper rim of said casing to provide a closed envelopeadapted to be evacuated.

The particular header shown, provides appropriate lead-in seals l4, l5for electrode leads !5, I1 respectively for an anode l8 and ignitor l9within the casing and supported from said header by said leads. Thelead-in sea s each include a glass or other insulating sleeve 20 bywhich the leads are kept electrically distinct from each other and fromthe casing. The an ode I8 is located toward the top of the casing, wellabove the bottom wall l2, whereas the ignitor I9 is located below theanode, preferably centrally of the casing, and is directed toward andterminates at its bottom in. the vicinity of said bottom wall. Saidignitor is shown. as relatively slender and tapers downwardly, with itsbottom end quite small. Said ignitor may be composed of materials asused for ignitors of the prior art, or may be of such other material ormaterials adapting it more especially to the present invention.

A sponge cathode, designated generally by numeral 2|, is provided insaid container and is of pan-cake shape, and situated upon the bottomwall I2 of the ignitron, preferably fitting the container at itsperiphery and frictionally or otherwise held permanently in fixedposition. The aforementioned lower small end of the ignitor l9 restsupon the upper surface of the sponge cathode 2| in constant contacttherewith, and as one means for maintaining such contact withoutdetriment to the lead-in seal I5, the lead-in I l for the ignitor,between the seal and the ignitor, is shown with a transversely extendingsection 22 which, with the rest of said lead-in, possesses adequateresiliency, supplemented by the weight of the ignitor, to accomplish thepurpose. The ignitor projects, from its contact on the sponge cathode,at right angles thereto and in a direction longitudinally of the casing.Mercury or other reconstructing liquid cathode material is appliedto'the sponge cathode 2| to the extent that said sponge will absorb themercury or the like without any excess remaining on the surface. Onemanner of thus charging the sponge body with mercury is to cleanse thesponge material until sufiiciently clean to be wetted by mercury andthen apply an excessive amount of mercury in the casing, whereupon thesponge will immediately fill with mercury, after which the free mercurywhich is not absorbed into the sponge can be poured off. The spongecathode 2!, with the absorbed mercury, constitutes the cathode of theignitron.

It has been suggested in copending application Serial No. 188,684, filedOctober 6, 1950, in the name of Donald E. Marshall, and assigned to thesame assignee as the present application, that any one of variousmaterials, sintered iron and sintered molybdenum being specificallyrecited, may be used for the sponge cathode. Each of these specificmaterials has its distinctive advantages and disadvantages. Forinstance, a sintered iron sponge absorbs mercury more readily andremains wetted by mercury longer under adverse conditions thanmolybdenum. But iron has the disadvantage of more rapid erosion underaction of the arc influenced by the necessarily high average current.Molybdenum dries up at its exposed surface far more rapidly than ironand is not as readily absorptive of mercury, and therefore may leavepools or drops of mercury on occasion on the surface of a molybdenumsponge cathode pending the delayed absorption of the mercury. Experienceteaches that the surface of a molybdenum sponge may dry up duringstand-by periods and also under conditions of temporary increase of gaspressure which may occur from overload. Excess mercury on the outside ofthe sponge is undesirable and detrimental since it may cause arc-backsor spontaneous ignition under shock. Furthermore, failure of mercury toreenter the sponge promptly, depletes the supply of mercury in thesponge where needed for arc-striking purposes. The lasting quality ofmolybdenum, however, is much superior to an iron sponge.

According to the present invention, I take advantage of the desirablecharacteristics of both iron and molybdenum in a sponge cathode. In theseveral exemplifications of the invention, each sponge cathodeillustrated comprises a body portion 23 of sintered iron or othermaterial having absorptive affinity for the reconstructing cathodefluid, such as the mercury above men tioned, and a sintered molybdenum,or equivalent material, arc-striking portion 24. The interstices betweengranules of molybdenum are smaller than between iron granules whichrender capillarity in molybdenum more pronounced than capillarity of theiron body, and capacity for mercury superior to molybdenum.

In the embodiments of the invention illustrated in Figs. 1 to 5,inclusive, the body portion 23 of the sponge cathode is shown relativelyfiat or thin of pan-cake shape to fit within the bottom portion of thecontainer fiatwise on the bottom wall thereof and frictionally 'held inplace as above described. In the showing of Figs. 1 to 4, inclusive. thearc-striking portion 24 comprises in whole or in part a smaller discthan said body portion, said smaller disc being embedded in said bodyportion 23 with the upper surfaces of said body portion and disc lyingin a common plane whereby both are exposed within the container only attheir upper faces. The disc is preferably located concentric to the saidbody, and is of less diameter and of less thickness than said body. Saiddisc is sintered compressed molybdenum or its equivalent having spongecharacteristic and highly resistive to erosion. By use of granules ofsubstantially equal size and applying evenly distributed pressure, thedisc may be thereby made to be effectively homogeneous throughout. Thecapillarity of the disc is determined by the degree of compactness, butthe material has ample sponge characteristic even when compressed underformulating force of several tons per square inch.

If so desired, the surface of the disc where the arc strikes, may bemade closer grained than the part of the disc not subject to direct arccontact. Thus, in Fig. 6, the disc is indicated as having its uppersurface of finer granules than are used to form the lower part of thedisc. Thereby the lower part of the disc provides larger inter sticesbetween particles'and constitutes a more ample reservoir for the mercuryin proximity to the arc-striking surface of the closer-grained material,so there will be a copious supply of mercury to and for the arc-strikingsurface of the disc.

The body portion 23 of the sponge cathode may be made in whole or inpart of compressed sintered iron granules an inherent characteristic ofwhich is more active absorption of mercury coming in contact therewiththan will occur with a similarly compressed sintered body of molybdenumgranules. An ignitron in use will condense mercury vapor on the sidewalls of the container, and that condensation forms in drops which rundown the wall and lodge upon the sponge cathode surface. By theprovision of a sintered iron sponge in the vicinity of the side wall ofthe container said surface will be in appropriate location to receiveand absorb the drops of mercury and thereby avoid presence or fiow ofmercury over the central arc-striking surface. The body portionfurthermore extends under the molybdenum disc at the center, andaccordingly will deliver the absorbed mercury to the under side of saiddisc during operation of the ignitron. By virtue of capillaritycharacteristic of the molybdenum, the supply of mercury from the ironbody is fed to the arc-striking surface of the molybdenum disc.

If so desired, and by any of a precautionary measure, it is within thescope of the invention to form the body portion 23 with its uppersurface comprising a graded thickness of molybdenum sponge 25 in thearea radially outward from the central disc of molybdenum. This had theadvantage that in event the arc spreads beyond the area of the disc,there still will be an erosive-resisting surface in contact with theare. The structure of this modification, Fig. 4, preferably provides adeeper thickness of the molybdenum 25 toward the center of the body thantoward the periphery thereof. The grading of the molybdenum thus affordsmaximum corrosion resistance in the area most likely to be affected bythe arc, and affords maximum absorptive characteristic toward theperiphery where the condensed mercury returns to the cathode.

If so desired, the graded molybdenum may be employed throughout thecentral portion of the body, and applied in appropriate depth andfineness of particles as shown in Fig. 5, to entirely replace theseparately formed disc of molybdenum.

Another modification is shown in Fig. 6, the disc there shown beinggraded as to thickness of the fine and coarser particles, the top layer26 of said disc having fine particles and the lower part of the dischaving coarse particles, and the intermediate portion is graded from thefine particles at the top to the coarse particles at the bottom. Thisconstruction has the advantage of the arc-resisting surface at the topand of furnishing a more copious supply of mercury thereto by thecapillarity derived from the larger interstices toward the bottom of thedisc, which in turn are supplied by the reservoir of mercury in theinterstices of the body 23.

Other modifications of the invention may be made of similar nature tothose above-described, so that further illustration is not deemednecessary for further indication thereof and as included within theterms of the appended claims.

I claim:

l. A vapor-electric device comprising a sealed casing having an anodetherein, a sponge cathode fixed in said casing, said. cathode comprisingdifferent sponge materials at different portions of said cathode andwith an extensive part of one making intimate contact with acorresponding part of the other, an ignitor in said casing and incontact with one of said sponge materials, and reconstructive cathodematerial absorbed in said sponge cathode.

2. A vapor-electric device comprising a sealed casing having an anodetherein, a sponge cathode fixed in said casing, said cathode comprisinga body of one sponge material and an arc-striking portion of a differentsponge material carried by said body, an ignitor in said casing and incon tact with said arc-striking portion of the sponge cathode, andreconstructive cathode material absorbed in said sponge cathode.

3. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode and with anextensive part of one making intimate contact with a corresponding partof the other, one of said materials being characterized by aflinity toabsorption of a reconstructing cathode material and the othercharacterized by its resistance to erosion from the effects of an arcthereon.

4. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode, one of saidsponge materials being carried by and of less surface area than theother and having greater resistance to erosion than the said onematerial from the effects of an arc thereon, said one material havinggreater affinity to absorption of a reconstructing cathode material thansaid other sponge material.

5. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode and with anextensive part of one making intimate contact with a corresponding partof the other, one of said materials being composed of sintered irongranules.

6. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode and with anextensive part of one making intimate contact with a corresponding partof the other, one of said materials being composed of sinteredmolybdenum granules.

7. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode and with anextensive part of one making intimate contact with a corresponding partof the other, one of said materials being composed. of sintered irongranules and the other composed of sintered molybdenum granules.

8. A sponge cathode for a vapor-electric device, comprising differentsponge materials at different portions of said cathode and with anextensive part of one making intimate contact with a corresponding partof the other, one of said materials comprising a larger body than theother, and said other being coaxially disposed with respect to thelarger, and both having surfaces exposed in the same general direction.

9. A sponge cathode for a vapor-electric device, comprising a pan-cakeshaped body portion of one material having an exposed upper surface, anda smaller disc of another material concentrically disposed to the bodyportion and having an upper face exposed in the same direction as saidupper face of said body portion.

10. A sponge cathode for a vapor-electric device, comprising a pan-cakeshaped body portion of sintered sponge iron having an exposed uppersurface, and a smaller disc of molybdenum embedded in said body and witha face thereof exposed in the same direction as and lying substantiallyin the same plane as said exposed face of the body portion.

11. A sponge cathode for a vapor-electric device, comprising a cake ofmetallic sponge ma.- terial having greater density at one portionthereof for constituting an arc-striking surface thereat resistive toerosion from the effects of the arc, and having another portion thereofof less density for promoting absorption of reconstructive cathodematerial condensation.

GERHARD LEWIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,128,861 Tonks Aug. 30, 19382,169,032 Slepian Aug. 8, 1939 2,218,386 Smith Oct. 15, 1940 2,432,513Depew Dec. 16, 1947 2,468,037 Clark Apr. 26, 1949

1. A VAPOR-ELECTRIC DEVICE COMPRISING A SEALED CASING HAVING AN ANODETHEREON, A SPONGE CATHODE FIXED IN SAID CASING, SAID CATHODE COMPRISINGDIFFERENT SPONGE MATERIALS AT DIFFERENT PORTIONS OF SAID CATHODE ANDWITH AN EXTENSIVE PART OF ONE MAKING INTIMATE CONTACT WITH ACORRESPONDING PART OF THE OTHER, AN IGNITOR IN SAID CASING AND INCONTACT WITH ONE OF SAID SPONGE MATERIALS, AND RECONSTRUCTIVE CATHODEMATERIAL ABSORBED IN SAID SPONGE CATHODE.